The association that represents thousands of FBI agents warned Thursday that a partial government shutdown could cause laboratory delays, reduce money for investigations and make it harder to recruit and retain agents.

The FBI Agents Association sent a petition to the White House and congressional leaders encouraging them to fund the FBI immediately. Friday will be the first day that the nearly 13,000 special agents will miss their paychecks.

“This is not about political for special agents. For special agents, financial security is national security,” Tom O’Connor, the association’s president, told reporters in a conference call.

Nearly 5,000 special agents, intelligence analysts and other staff are currently furloughed. Those absences mean FBI operations are understaffed and subject to delays, including at the FBI lab. And the lapse means fewer tools, such as informants or undercover operations, are available for investigations.

“We have people are not being able to come to work, which means they’re not able to do the work,” O’Connor said. “Which means we’re going to have a backlog.”

O’Connor also said the shutdown may cause delays in agents being able to get or renew security clearances, potentially disqualifying some agents from continuing to participate in certain cases, and could make it harder to recruit and retain who could find better paying or more stable jobs outside the government.

The association has more than 14,000 active duty and retired special agent members.